1. Field of the Invention
This invention relates to a diagnostic and inspection system for viewing objects where access to the object is limited such as where minimally invasive techniques are preferable, and more particularly to a diagnostic color video system for medical and/or industrial applications needing miniature endoscopes, i.e. diameter at the distal end of less than 2 mm.
2. Informational Disclosure Statement
Endoscopes have many industrial applications and medical applications, and are typically used to access and view objects located within apparati or bodies. In an industrial application, an endoscope, generally called a borescope, may be used to view the hidden components of an internal combustion engine; in a medical application, an endoscope may be used for minimally invasive viewing for diagnosis. A medical endoscope can also be used in conjunction with the delivery of drugs to, or other treatment at a specific site or with the cutting or ablation of diseased or damaged tissue.
An endoscope typically includes a body having a distal end for insertion and image collection; a lumen or passage for conveying wiring, an optical waveguiding element for conveying light, (e.g. optical fibers) and perhaps mechanical cables to the distal end; and a proximate end for manipulation by the operator and for access to the elements carried to the distal end.
Optimally, an endoscope is small and lightweight such that the distal end can be easily inserted into narrow internal passages and can be readily positioned by manipulation of the proximate end; flexible, such that the endoscope body readily follows the contours of internal passages; capable of manufacture at reasonable cost; and capable of collecting considerable diagnostic information. In practice, designing an endoscope that incorporates all of the above features can be difficult. Standard endoscopes for medical applications typically have 3 mm outer diameter with newer ones lying in the range of 2-3 mm. Industrial endoscopes currently are generally larger in diameter.
For example, an endoscope typically illuminates the object to collect an image thereof. Accordingly, powerful light sources conveying light over large diameter (i.e., low-loss) fiber bundles, large collection optics and large diameter coherent fiber bundles for conveying the collected image from the distal to the proximate end of the endoscope are commonly used in standard endoscopes. In many cases, the required maneuverability and flexibility dictate that the illumination fiber bundle has large numbers of small diameter fibers, and that the imaging fiber optic bundle likewise uses large numbers of small diameter fibers. Large numbers of small fibers are normally required because smaller dimensioned fibers result in higher loss. Using many small diameter fibers thus provides flexibility but the fiber bundle remains large because of their higher loss, which would reduce illumination. Additionally, while small diameter fibers can improve resolution in the image bundle, the manufacture of the coherent bundle becomes more complex as the number of individual fibers increases.
A color image can convey more diagnostic information than a black-and-white image. However, bulkier, more sophisticated and more expensive signal processing hardware is typically associated with producing a color image.
Prior attempts are documented in patents such as U.S. Pat. No. 4,653,478 issued to Nagasaki et al., and U.S. Pat. No. 4,261,344 issued to Moore et al. In these approaches, a charge coupled device (CCD) positioned at the distal end of the endoscope converts the image of the object to electrical impulses, which are transmitted within the body of the endoscope by wires that are less bulky than fibers carrying the image. A color image is obtained from the device by sequentially illuminating the object with light obtained by sequentially placing appropriate filters in front of a white light source. Multiplexing the image data creates an RGB sequence. Full-color video pictures are thus obtained.
Disclosed in each of these patents, however, are standard multi-wavelength light sources, which either use filters to select a broad color region or colored light sources. For example in the Nagasaki et al. patent, the choice of sources are; a white light with appropriate color filters to get sequential RGB illumination, or red, green and blue lamps, or alternatively illuminous diodes, emitting light of the 3 primary colors. In the Moore patent, bulky strobe light sources convey light to the object via separate bundles of fibers, thus reducing the maneuverability and flexibility of the endoscope. Each of the colored light sources, including the filtered white light, emits and transmits a relatively broad distribution of wavelengths within the specified color region to the distal end of the endoscope. This is good in terms of reconstitution for true color vision, but these sources are generally of moderate power intensity, at best. The transmission elements, connecting light source to illuminated site, need to contain large core fibers or very large numbers of small core optical fibers to allow sufficient energy density to be seen and recorded. The only alternative to these schemes, is that Nagasaki et al. suggests that illuminous diodes could be used directly attached to the side of the detector chip. This would likely keep the tip larger than might be preferred and also, for the medical applications, could leasd to introducing metals and semimetals to the patient""s body that would best be kept away from body tissues and fluids.
The prior art would not recommend using laser sources for color video systems, even though they have high brightness, because a laser normally emits a very limited number of wavelengths around its main operating wavelength, i.e. possibly 2-5 nm or less about the operating wavelength, giving a specific shade of red rather merely red. Luminous diodes in contrast can produce broad enough light to span the blue-green region of the spectrum as described in U.S. Pat. No. 5,657,165 issued to Karpman, so that sequential filtering with blue and green filters can be employed to project blue and then green beams, respectively.
Accordingly, as an improved endoscope would be a useful and welcome advance, it is an object of the present invention to address one or more of the aforementioned drawbacks and disadvantages of the prior art.
Other general and specific objects of the invention will in part be apparent and will in part appear hereinafter.
It is an object of the present invention to provide a color video diagnostic system for mini-endoscopes having a black-and-white video chip for collecting an image of the object being viewed and a laser diode illumination source for providing different colors of light for illuminating the object.
It is another object of the present invention to include a diagnostic laser diode light source having a wavelength selected for fluorescing an imaging agent for imaging a selected feature of an object being viewed. The object is exposed to an imaging agent, which is selected to target a specific feature of the object and which is known to be excited by a predetermined wavelength of light to fluoresce. The diagnostic laser diode light source is selected to operate at the predetermined wavelength, which may be within the near infrared spectral region. The feature, if part of the object, can be more readily distinguished on the video display of the color signal.
Briefly stated, the present invention provides a color video diagnostic system for mini-endoscopes for viewing features of objects where access to the object is limited or where minimally invasive techniques are preferable, such as in medical or industrial applications. A black-and-white video chip mounted at the distal end of an endoscope body images an object sequentially illuminated by laser diode light sources having different wavelengths. More than one laser diode may be used within a color region to provide truer color representations. A controller controls the laser diode light sources for sequentially illuminating the object by color, and a video processor responsive to the controller receives signals from the black-and-white video chip for producing a color data signal. A display displays a color image of the object. At least one diagnostic laser diode light source, which can be tunable, may be included for enhancing selected features of the object being viewed, and it may emit in the visible, near infrared, or infrared wavelength regions. A beam-combining element can be included for combining the light beams from the laser diode light sources for provision to a fiber light transport element for transporting the light to illuminate the object.
The invention thus advantageously incorporates laser diode light sources, which have exceptional brightness, particularly when diode lasers or diode pumped solid state lasers or directly frequency doubled laser diodes are employed with a black-and-white video chip, that is less expensive and bulky than a color video chip, to provide an improved endoscope. The brightness of the laser diode sources, as well as the beam combiner, allow use of a fiber transport element having fewer optical fibers with at most one per laser source, thereby reducing the diameter of the fiber xe2x80x98bundlexe2x80x99 and of the outer casing for the system and enhancing the flexibility of the endoscope. In one embodiment, the fiber light transport element can be a single optical fiber.
Incorporation of the diagnostic laser diode light source thus advantageously provides a more versatile mini-endoscope with increased diagnostic capabilities, without adding significant bulk or weight to the mini-endoscope, thus maintaining maneuverability and ease of use.
These and other features of the invention are more fully set forth below.